Vehicle bumper

ABSTRACT

A vehicular bumper comprising means for absorbing impacts by a combination of springs and hydraulic energy absorption activated by mechanical linkage that increases the rate of energy absorption and resistance to impact as functions of the displacement of the bumper relative to the vehicle.

United States Patent [191 Applegate 1 VEHICLE BUMPER ['76] Inventor:Lindsay M. Applegate, 7045 Molokai Drive, Paradise, Calif. 95969 [22]Filed: Feb. 14, 1972 [21] Appl. No.: 225,724

[52] US. Cl. 293/84 [51] int. Cl. B60r 19/04 [58] Field of Search 293/84[56] References Cited UNITED STATES PATENTS 1,386,452 8/1921 Dotzer etal. 293/84 1,777,342 10/1930 Williams 293/84 IMPACT Nov. 13, 19731,792,157 2/1931 Franke 293/84 1,435,100 11/1922 Bilterman et a1.1,497,653 6/1924 Coote Primary Examiner-Gerald M. Forlenza AssistantExaminer-Robert Saifer [57] ABSTRACT 3 Claims, 1 Drawing Figure VEHICLEBUMPER This invention is concerned with the front and rear protectivemembers of vehicles subject to impact with other vehicles or obstacles.There have beenmany different forms of front and rear vehicle bumperscapable of absorbing some of the energy of impact and thereby protectingthe vehicle to some extent from damage. The majority of bumpers onvehicles have been attached to the frames of the vehicles with meansranging from solid bolting to some form of spring or other flexiblemeans capable of absorbing some energy.

Some of the bumpers presently provided on automobiles and trucks aresolidly bolted to the vehicle frames, or attached by means with a smalldegree of spring or flexibility. A solid mounting absorbs practically noenergy and transmits the energy of impact to the vehicle frame. A springsupport incurs deflection in impact converting kinetic energy topotential energy which is transmitted to the vehicle frame and whichcases the force of impact on the vehicle. If the flexible mounting ofthe bumper incorporates an energy conversion and absorption member, someof the energy of impact can be converted to heat and the total energytransmitted to the vehicle frame is thereby decreased. Motor vehicleshave been provided with hydraulic bumpers in which hydraulic resistanceto bumper displacement increases with piston travel. These have hadhydraulic cylinders set so that their piston travel is the same asbumper travel and therefore the length of the cylinder is limited to thedistance permitted in bumper displacement.

In the design of vehicle bumpers, esthetic requirements, spacelimitations and cost of manufacture and maintenance are importantconsiderations. The distance provided for movement of the bumperrelative to the frame is a dominant factor in the design of mountingsand energy-absorbing means that may be involved. In the prior art thereare bumper systems with transverse shock-absorbing elements intended toeconomize space lengthwise of vehicles. I

The principal object of my present invention is a vehicle bumper thatcan absorb energy effectively for the protection of a vehicle in impactwith minimum travel space between the bumper and vehicle. A secondobject is a bumper that will protect a vehicle, be adaptable to estheticvehicular design and be produced at moderate expense. Another importantobject is to provide means whereby, in a bumper system, variable ratehydraulic resistance to impact and displacement is controlled bymechanical connections between bumper bars and hydraulic energyabsorbers.

What constitutes this invention is described in the followingspecification with respect to the accompanying drawing and the novelfeatures thereof are succiently defined in the appended claims.

In FIG. 1, which is schematic and only suggestive of scale, and whichshows only half of a complete bumper system assemblage, l is the bumperproper referred to also as the bumper bar, and for brevity as bumper,the element of the assemblage that receives the impact of a collision.The assemblage is supported on the vehicle frame 2 which may be anyconventional form adapted to accommodate the other components of thebumper assemblage. Y

The principal energy-absorbing elementof the system is a hydrauliccylinder 3 attached at the closed end of the cylinder to the frame 2 bya pivoted bracketed joint 9. The cylinder 3 includes a spring 4 anddamping fluid 5, together with a piston rod 17, piston 18 and an orificein the piston for damping effect and energy absorption in response tomovement of the piston and rod.

A second pivoted and bracketed joint 6 is provided on the frame tosupport a mechanical lever 10 pivoted and connected to the outside end 11 of the cylinder piston rod 17.

A spring 8 is provided optionally between the bumper 1 and frame 2. Thisspring is, in effect, in parallel with the spring 4 in cylinder 3. It ispossible to omit either spring 4 or spring 8, relying on only one springto perform spring function in the bumper operation.

A second mechanical link 12 is connected at a pivoted joint 13 to thebumper l and to lever 10 at pivoted joint 14. A rubber, or similarbracketed stop 15 is provided optionally for maintaining lateralpositioning and stability relativeto frame 1. Either stop 15, or spring8, particularly if spring 8 includes a leaf spring component, as shown,with inherent capability of lateral stabilization, can contribute tolateral stability, although the leaf spring construction of spring 8 ispreferred. Some arrangement for lateral stability is required, inasmuchas link 12 would permit lateral movement of bumper 1 relative to frame2.

In the operation of this bumper system, an impact on bumper l compressesspring 8 permitting bumper 1 to move in the direction of, and relativeto, frame 2. Link 12 is carried with bumper 1 so that lever 10 isrotated around pivoted pivot 6. The movement of lever 10, beingrestrained at pivot 6, is in a rotational path in which the outside end11 of the cylinder piston rod 17 is carried by lever 10 in a circularpath indicated by the arrow 7. A 'second rubber or similar stop 16 isprovided optionally to limit the maximum travel of lever 10. In FIG. 1the relative positions of cylinder 3, lever 10 and the associatedelements 3, 4 and 17 are shown by broken lines illustrative of theirpositions when bumper l is in the rearward location after impact.

The movement of bumper 1 relative to frame 2 is resisted by spring 8which stores energy and decreases the impact transmitted to frame 2 butreturns to stored energy to the system after the impact has subsided. Sosimiarly, spring 4 in cylinder 3 stores and returns energy of impact.These springs act to restore the bumper and the associated parts of thesystem to their original positions after impact.

Link 12, following impact on bumper 1, moves rearward with a velocitydetermined by the force of impact and resistance offered by cylinder 3.Lever 10 rotates about pivot 6 at a velocity determined by the velocityof link 12. This rotational velocity may be relatively high and pivot11, connecting lever 10 to piston rod 17, will be impelled at a velocityin the circular path shown in FIG. 1 determined in part by the ratio ofdistance from pivot 6 to pivot 11, relative to the distance from pivot 6to pivot 14. The relative velocity of piston rod 17 in cylinder3,however, beginning at impact with lever 10 colinear with piston rod 17is relatively low, functionally approximating the product of the anguarvelocity and length of lever 10 and the tangent of the angle throughwhich lever 10 has rotated from the initial position colinear withpiston rod 17. Thus in dis placement from original position, thevelocity of piston rod 17 and'piston 18 in cylinder 3 increases as afunction of angular position of lever 10 and linear velocity of link 12and bumper 1. The increased velocity of piston 18 with a fixed orificefor flow of hydraulic fluid increases the hydraulic resistance to themovement of bumper l as a function of distance and velocity indisplacement of bumper 1 from original position. The result is that thehydraulic resistance to bumper impact is relatively low initially butincreases rapidly in resistance and energy absorption as the bumper bar1 is forced toward the vehicle frame 2. The desire in impact control isto resist the force of impact gradually so that frame 2 incurs minimumforce while the movement of bumper 1 is arrested and stopped within areasonable distance prior to impact impingement of bumper 1 on frame 2.The circular motion of lever begins at a point where lever 10 iscolinear with the axis of piston rod 17, hence accelerates piston rod 17at a rate starting at zero and increasing as link 10 is rotated untillever 10 has rotated nearly 90 degrees as shown in the broken lines inFIG. 1 when the piston rod will will be pulled at maximum velocity andconsequently at maximum hydraulic resistance in fluid 5 in cylinder 3.This piston movement at increasing velocity with correspondingincreasing resistance will arrest the movement of bumper l graduallywith increasing force while absorbing energy in cylinder 3 where theenergy of impact is converted to heat through the medium of fluidfriction. That is to say, the impact on bumper 1 is absorbed anddecelerated gradually.

There are several advantages of the construction shown in FIG. 1compared with alternative arrangements such as a cylinder connected tothe bumper so that the piston movement would be the same as that of thebumper relative to the frame. In FIG. 1 a relatively long hydrauliccylinder comparable in shape and dimensions with conventional automotiveshock absorbers can be used. The linkage comprising lever 10 and link 12translates a short movement of bumper l relative to frame 2 into a muchgreater movement of piston 17. For example, if it were required torestrict the movement of bumper l to a limit of 5 cm relative to frame2, lever 10, if made cm long, with the distance between the pivot at 6and the pivot at 14 set at 5 cm, the piston 17 would be moved more thanfour times the travel permitted between bumper l and frame 2. Thisprovides for more readily controlled hydraulic resistance than in ashort cylinder. Another advantage is that the increasing velocity ofpiston 17 progressively increases hydraulic resistance as a function ofdisplacement of bumper 1 relative to frame 2 and this substitutesvelocity control for throttling control as would be required for a shortcylinder whose piston movement would be directly the same as themovement of bumper 1 relative to frame 2. Another advantage of theconstruction shown in FIG. 1 is that the transverse positioning ofcylinder 3 in the vehicle frame permits the use of a long cylinder morereadily than if a longitudinal emplacement were used. The arrangementshown can be designed so that a minimum of space at the front or rear ofa vehicle will accommodate the assemblage.

It will be apparent to those skilled in this art that the fundamentalprinciples principles employed in this invention includes the increaseof resistance developed by increase of velocity at a rate determined byapproa single cylinder with attachment at the middle of bumper 1 insteadof using two assemblages as implied in FIG. 1, and other details ofdesign, are feasible in the adaptation of the principle to variousarrangements of vehicular construction.

In the wording of this specification and of the claims a hydraulicdamper means cylinder 3, fluid 5, and the associated operational parts.An energy absorbing medium means fluid 5 in conjunction with piston 18in cylinder 3. Vehicle bumper means the system as described in FIG. 1.Bumper bar means bumper 1 as indicated in FIG. 1. In describing themechanical action of bumper bar 1 link 12, lever 10, piston rod 17 andcylinder 3, the trigonometric relationship of the several parts isuseful. If bumper bar 1 is moved toward frame 2 at a uniform speed, link12 is moved also at uniform speed. The end of link 12 moves at pivot 14in a circular arc of relatively small radius. Lever 10 at pivot 14 alsotravels in the same small circular arc, but the outer end of lever 10 atpivot 11 travels in the circular arc of greater radius indicated by thearrow in FIG. 1, ultimately to the final position indicated by thebroken lines. The velocity of rotation of lever 10 is increased asbumper l and link 12 are forced in the direction of frame 2 assuminguniform velocity of bumper l. The end of piston rod 17 at pivot 11starts, relative to cylinder 3, at zero speed inasmuch as lever 10 androd 17 are colinear, and, assuming constant velocity of bumper 1, thespeed of rod 17 relative to cylinder 3 is accelerated approximately inproportion to the trigonometric tangent of the angle through which lever10 has become displaced from the original colinear position shown insolid lines in FIG. 1. The speed of piston rod 17 and piston 18 incylinder 3 is approximately the product of the linear velocity of bumperbar 1 and the tangent of the angle through which lever 10 has moved fromthe initial position. The degree of approximation of the actual speedsand displacements to the mathematical is precise at zero displacementbut decreases as the displacement increases, due to the angular rotationof cylinder 3 about pivot 9 and to the necessary departure of mechanicalparts from mathematical lines. 1

I claim:

1. A vehicle bumper system comprising a bumper bar supported on avehicle frame and adapted to be displaced upon impact toward said frame,a link pivotally connected at one end to said bumper bar and at theother end to a lever pivoted at one end on said vehicle frame and at theopposite end to the piston of a hydraulic damper cylinder pivoted at theend of said cylinder to said vehicle frame, said link being connected tosaid lever between the middle of said lever and the pivot of said leverto said frame, whereby in operation said lever is initiallysubstantially parallel to said bumper bar and perpendicular to said linkand colinear with said piston and cylinder and upon impact and movementof said bumper bar said lever is rotated about said pivot to frameimparting movement to said piston relative to said cylinder at anaccelerating rate as said bumper bar is moved toward said vehicle frame.

2. In a vehicle bumper, the combination of a bumper bar, a linkconnected perpendicular thereto and connected to a lever substantiallyparallel to said bumper bar pivoted at one end on the vehicle frame andat the other end to the piston of a hydraulic damper cylinder, said linkbeing connected to said lever between the middle thereof and said pivoton said vehicle frame,

nected, at the end opposite the piston rod, to said vehicle frame, and alink connecting said bumper bar to said lever between the middle thereofand the end pivoted on said vehicle frame, whereby displacement of saidbumper bar relative to said frame rotates said lever around the pivot onsaid vehicle frame producing a displacement in said hydraulic cylinderwhich increases at a rate which is approximately determined by theproduct of said displacement of said bumper bar and the tangent of theangle of displacement of said lever.

1. A vehicle bumper system comprising a bumper bar supported on avehicle frame and adapted to be displaced upon impact toward said frame,a link pivotally connected at one end to said bumper bar and at theother end to a lever pivoted at one end on said vehicle frame and at theopposite end to the piston of a hydraulic damper cylinder pivoted at theend of said cylinder to said vehicle frame, said link being connected tosaid lever between the middle of said lever and the pivot of said leverto said frame, whereby in operation said lever is initiallysubstantially parallel to said bumper bar and perpendicular to said linkand colinear with said piston and cylinder, and upon impact and movementof said bumper bar said lever is rotated about said pivot to frameimparting movement to said piston relative to said cylinder at anaccelerating rate as said bumper bar is moved toward said vehicle frame.2. In a vehicle bumper, the combination of a bumper bar, a linkconnected perpendicular thereto and connected to a lever substantiallyparallel to said bumper bar pivoted at one end on the vehicle frame andat the other end to the piston of a hydraulic damper cylinder, said linkbeing connected to said lever between the middle thereof and said pivoton said vehicle frame, whereby displacement of said bumper bar relativeto said vehicle frame rotates said lever at an angular rate whichincreases with increased bumper bar displacement thereby actuating saidhydraulic damper relatively slowly when said bumper displacement beginsand increasing the rate of hydraulic damping as a function of bumperdisplacement at any rate of increase of bumper displacement.
 3. In avehicle bumper, a bumper bar, a lever pivoted at one end on the vehicleframe and at the other end to the piston rod of a hydraulic cylinderpivotally connected, at the end opposite the piston rod, to said vehicleframe, and a link connecting said bumper bar to said lever between themiddle thereof and the end pivoted on said vehicle frame, wherebydisplacement of said bumper bar relative to said frame rotates saidlever around the pivot on said vehicle frame producing a displacement insaid hydraulic cylinder which increases at a rate which is approximatelydetermined by the product of said displacement of said bumper bar andthe tangent of the angle of displacement of said lever.